By the inclusion of Azazel, his character will no doubt be central to Mystique's development in this film...in X1-X3 we have little of her backstory, only us fan boys/girls knew that Kurt/Nightcrawler is her son,(when X2 was released Rebecca mention in Singer's X3 they were going to develop Mystique more, so this could have led up 2 the reveal of them being mother/son)...

I'm thinking that Azazel & Mystique will be potrayed as lovers, and Kurt will be a young infant (maybe using cgi, think Avatar), a human element comes into play which seperates the family, maybe Azazel gets killed trying to protect them, which causes Mystique to give up Kurt, fearing that no child should live a life being hunted, which could lead to the circus where she trusts someone maybe Margali to raise him....from their she meets Eric/Charles, but by this time she is so far gone that she has developed a pure hatred for humanity and when the split happens she goes w/Eric and from we here the audience will understand her motives in X1-X3